I don't think that we can lay the blame for agression in children on the laps of the media, that's all down to parenting, if a child only only learned one effective way to express itself then that's the one it's going to use but I do think the glorifying of violence has an effect, we know for a fact that the portrayal of Smoking as being cool in the media led to a major increase in tobacco sales so why shouldn't portraying violence as cool have the same effect.